the server can't ssh,but ping is ok

What is the IP address? Does it ping? What about your firewall?

I met same problem too.

I issued a ticket and the service guy said from his end, it seems normal.

can use the Linode lish connect to server.
Is that because this IP is a contaminated one?

Hey there! It's unlikely this is due to a "contaminated" IP address. It's likely this is an issue with either the firewall or the service. Following some of the troubleshooting steps in this Community Site post should help point you in the right direction. Otherwise, providing specific errors you are experiencing should help provide a little more context to what is wrong and we might be able to provide a more accurate answer.